Test numpy<->ds9 with 3D arrays (issue #59) [skip appveyor]

[montefra]

This PR addresses issue #59

• [x] test to verify issue
• [x] resolve issue

I have added a test_3d.fits file replicating 3 times the test.fits in the z-direction. This should be enough to test the problem

[montefra]

@ericmandel : commit aa73eae28ccdeed20c8d2af150c7d17466194d7a should solve issue #59 .

However when creating a 3D array I came across the fact that python uses C ordering while fits uses Fortran ordering.

This means that:

numpy shape	NAXIS1	NAXIS2	NAXIS 3
(10, 8)	8	10
(3, 10, 8)	8	10	3

So I:

1. replaced the symmetric 15 x 15 test fist with asymmetric 8x10 fits images
2. flipped xdim/ydim the set_np2arr function.

get_arr2np already does the correct thing.

If you want to double check the ordering open python/ipython and do:

In [1]: from astropy.io import fits
In [2]: hdus = fits.open('my/fits/file')
In [3]: hdus[0].data.shape
In [4]: hdus[0].header

Can you please check the changes?

[ericmandel]

I tested this on a real data cube and it looks like it does what you want:

However, I can't comment on whether this is what numpy users expect, since I don't use Python/numpy. I think you should merge the PR but just keep in the back of your mind that there might be questions.

[montefra]

Thank you for checking. As I wrote, I think that this is the expected behaviour. Anyway I'll keep in mind

[ericmandel]

I'm confident you have it right. My comment is rooted in the fact that several years ago, I had it coded one way and then was told it needed to be the other way. So clearly I don't know which end is up with numpy!

[montefra]

So clearly I don't know which end is up with numpy!

I also never remember which way is numpy indexed. I always end up in a ipython session to do some test.